1. Field of the Invention.
The present invention relates to a device for bridging over the expansion joints in roadways and the like, especially in bridge roadway.
2. Description of the Prior Art.
Known devices for bridging over expansion joints comprise sliding and rubbing components which render possible the opening and closing of the joint. Deterioration of the mobility under the action of dirt, corrosion and wear can cause these known devices to become useless in time. Moreover such designs require very great precision in production.
Another known device according to Swiss Pat. No. 440,360 consists of thin-walled carrier rods of zig-zag or undulatory form arranged in the direction of movement which are connected with beams extending parallel with the joint edges. Such a device has the disadvantage that it cannot be made watertight, since the two-dimensional movements of the gaps render secure sealing impossible. Moreover the carriers with undulatory or zig-zag course with thin walls must be made easily deformable, which is not possible in the case of wide joints requiring strong rods. The requisite bearing capacity and elasticity can be achieved only limitedly with small joints.
A further device according to U.S. Pat. No. 2,797,952 comprises plates which are supported on trusses of articulated rods connected with the joint edges. Unavoidable forces acting in the transverse direction of the roadway cannot be taken up. The joints, which are heavily stressed under the traffic load, are prone to wear and in time troublesome chattering noises are to be expected. The design requires high production precision. Arrangement of seals in the plate interspaces is possible. A further device according to U.S. Pat. No. 3,904,302 comprises a plurality of rigid strips and elastomeric strips between adjacent rigid strips which extend longitudinally through the gap. Upper ends of the legs are connected to the rigid strips. Lower ends of the legs are interconnected with each other in pairs whereby adjacent legs form a pair and an elastically yielding structure. This design has the disadvantage that the legs and the elastically deformable rigid strips must take up the bending moments from the traffic load. For this reason this system without additional supporting can be used sensibly and economically only to bridge over minor joints.